US20240124373A1 - Co conversion control for multistage fischer-tropsch syntheses - Google Patents

Co conversion control for multistage fischer-tropsch syntheses Download PDF

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US20240124373A1
US20240124373A1 US18/555,047 US202218555047A US2024124373A1 US 20240124373 A1 US20240124373 A1 US 20240124373A1 US 202218555047 A US202218555047 A US 202218555047A US 2024124373 A1 US2024124373 A1 US 2024124373A1
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Julian Baudner
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Ineratec GmbH
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    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G2/00—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon
    • C10G2/30—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen
    • C10G2/32—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts
    • C10G2/33—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used
    • C10G2/331—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used containing group VIII-metals
    • C10G2/332—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used containing group VIII-metals of the iron-group
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C1/00—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon
    • C07C1/02—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon from oxides of a carbon
    • C07C1/04—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon from oxides of a carbon from carbon monoxide with hydrogen
    • C07C1/0425—Catalysts; their physical properties
    • C07C1/043—Catalysts; their physical properties characterised by the composition
    • C07C1/0435—Catalysts; their physical properties characterised by the composition containing a metal of group 8 or a compound thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
    • B01J8/02—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds
    • B01J8/04—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds the fluid passing successively through two or more beds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
    • B01J8/02—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds
    • B01J8/04—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with stationary particles, e.g. in fixed beds the fluid passing successively through two or more beds
    • B01J8/0492—Feeding reactive fluids
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C1/00—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon
    • C07C1/02—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon from oxides of a carbon
    • C07C1/04—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon from oxides of a carbon from carbon monoxide with hydrogen
    • C07C1/0455—Reaction conditions
    • C07C1/046—Numerical values of parameters
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C1/00—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon
    • C07C1/02—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon from oxides of a carbon
    • C07C1/04—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon from oxides of a carbon from carbon monoxide with hydrogen
    • C07C1/0485—Set-up of reactors or accessories; Multi-step processes
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2/00—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms
    • C07C2/02—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by addition between unsaturated hydrocarbons
    • C07C2/04—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by addition between unsaturated hydrocarbons by oligomerisation of well-defined unsaturated hydrocarbons without ring formation
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G2/00—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon
    • C10G2/30—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen
    • C10G2/32—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts
    • C10G2/34—Apparatus, reactors
    • C10G2/341—Apparatus, reactors with stationary catalyst bed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/00002—Chemical plants
    • B01J2219/00027—Process aspects
    • B01J2219/0004—Processes in series
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2523/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00
    • C07C2523/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of the iron group metals or copper
    • C07C2523/74—Iron group metals
    • C07C2523/75—Cobalt
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G2300/00—Aspects relating to hydrocarbon processing covered by groups C10G1/00 - C10G99/00
    • C10G2300/10—Feedstock materials
    • C10G2300/1022—Fischer-Tropsch products

Definitions

  • the present invention relates to methods for operating Fischer-Tropsch syntheses for the production of long chain hydrocarbons and to plants for carrying out these methods, whereby the CO conversion is controlled and/or the catalyst deactivation is compensated.
  • Fischer-Tropsch synthesis used to produce hydrocarbons has been known for many decades.
  • a synthesis gas consisting predominantly of carbon monoxide (CO) and hydrogen (H 2 ) is converted to hydrocarbons by heterogeneous catalysis in a synthesis reactor.
  • the products in the outlet stream of such a synthesis reactor essentially comprise four fractions:
  • the synthesis gas for such FTS comes, for example, from gasification of biomass, from synthesis gas generation from fossil starting materials (natural gas, crude oil, coal), or from electricity-based processes (conversion of electrolytically generated H 2 as well as CO 2 ).
  • a central characteristic of FTS is the fact that a very broad product spectrum (from C 1 to >C 100 ) is always produced.
  • the increase in selectivity of a certain main product is of interest.
  • Long-chain, waxy hydrocarbons can, inter alia, be fed to industry for material use, or serve in the conventional refinery process as a feedstock for high-quality fuels with a low CO 2 footprint.
  • the proportion of this wax phase one of the highest-value products of synthesis, is only in the range of a few percent.
  • the object of the present invention was to overcome the above-described disadvantages of the prior art and to provide a method for operating an FTS with which the above problems can be effectively countered.
  • ambient temperature means a temperature of 20° C. Temperature indications are in degrees Celsius (° C.) unless otherwise indicated.
  • Pressure data in the context of the present invention mean absolute pressure data, i.e. x bar means x bar absolute (bar a ) and not x bar gauge.
  • long-chain hydrocarbons are understood herein hydrocarbons with at least 25 carbon atoms (C 25 ).
  • the long-chain hydrocarbons with at least 25 carbon atoms can be linear or branched.
  • shorter-chain hydrocarbons are understood herein hydrocarbons with 5 to 24 carbon atoms (C 5 -C 24 ).
  • the shorter-chain hydrocarbons with 5 to 24 carbon atoms can be linear or branched.
  • short-chain hydrocarbons are understood herein hydrocarbons with 1 to 4 carbon atoms (C 1 -C 4 ).
  • the short-chain hydrocarbons with 4 carbon atoms can be linear or branched.
  • the term “comprising” can in particular also mean “consisting of”.
  • a formulation “comprising element “A” and element “B”” is to be interpreted in such a way that further elements (“C”, “D”, . . . ) are permitted, but also that in a preferred embodiment only the elements “A” and “B” may be present.
  • a subject matter of the present invention is a method of operating a Fischer-Tropsch synthesis comprising the steps of,
  • the target products that are produced by the method according to the invention preferably comprise the solid, waxy phase as well as the liquid, hydrophobic phase, but in particular the solid, waxy phase of hydrocarbons.
  • these can be supplied to industry for material use, or used in the conventional refinery process as a starting product for high-quality fuels.
  • the method according to the invention has, among others the advantage that the yield of long-chain hydrocarbons is increased.
  • the synthesis gas is first fed into the first fixed-bed synthesis reactor.
  • a part of the synthesis gas reacts under Fischer-Tropsch conditions to form hydrocarbon compounds.
  • parts of the hydrocarbons are separated from the rest of the material stream.
  • the products remaining in the stream, which leave the product separation, are fed to the second fixed-bed synthesis reactor.
  • the material stream fed to the second fixed-bed synthesis reactor thus preferably consists of hydrocarbons, preferably short-chain and/or shorter-chain hydrocarbons, residual reaction water, unreacted synthesis gas and by-products of the first synthesis, as well as impurities (e.g. N 2 ).
  • the synthesis reactors used in the method according to the invention are fixed-bed synthesis reactors.
  • a fixed-bed synthesis reactor in the sense of the present invention is a reactor in which at least one, preferably exactly one, bed of catalyst particles is arranged.
  • a support (mounting), on which the catalyst is arranged may be provided in its interior.
  • the reactor is flowed through by gases and/or liquids (fluids) to be reacted, the reaction takes place at the catalyst (contact) (heterogeneous catalysis).
  • the architecture of the first and second fixed-bed synthesis reactor is not limited in principle.
  • the first and second fixed-bed synthesis reactors have essentially the same architecture.
  • the fixed-bed synthesis reactors used are preferably microstructured fixed-bed synthesis reactors. This allows the size of the overall plant to be varied to a much greater extent than in the plant concepts presented so far.
  • Microstructured reactors are preferably characterised by the fact that they have a large inner surface and can thus ensure particularly efficient heat transfer. By that exothermic or endothermic reactions in particular can be operated in a well-controlled manner. In a generally accepted but not legally binding definition, the internal structures of microstructured reactors are smaller than 1 mm in at least one dimension.
  • microreactors such as those described, for example, in DE 10 2015 111 614 A1, in particular paragraphs [0023] to [0028] and FIGS. 1 to 4.
  • the present invention does not use reactors with catalyst structures as described in WO 2004/050799 A1, since these are large catalyst structures that do not comprise individual catalyst particles.
  • a fixed-bed synthesis reactor may comprise one or more apparatuses connected in parallel, whereby these are preferably characterised by an identical architecture.
  • one or more further reaction stages are connected serially downstream of the first and/or second reaction stage, comprising a fixed-bed synthesis reactor and a product separation.
  • first and second fixed-bed synthesis reactors further first and second synthesis reactors, preferably further fixed-bed synthesis reactors.
  • one or more synthesis reactors, preferably further fixed-bed synthesis reactors are connected in parallel to the first and second fixed-bed synthesis reactors in order to increase the overall capacity of the plant.
  • These reactors connected in parallel may each be provided with their own product separations, or the product stream may be combined prior to product separation and then passed through a common product separation.
  • synthesis gas is added exclusively to the first fixed-bed synthesis reactor.
  • the mixture comprising short-chain and shorter-chain hydrocarbons exiting the first fixed-bed synthesis reactor and optionally processed via a product separation is not considered as synthesis gas in the context of the present invention, even if it contains hydrogen and carbon monoxide.
  • Common catalysts used in FTS include the transition metals cobalt, nickel, iron and/or ruthenium. Catalysts containing various mixtures of the aforementioned metals or promoters, for example from the lanthanide group, are also known and used for the reaction. As supports usually high temperature stable materials, which Al 2 O 3 , ZrO 2 , SiO 2 , TiO 2 , various ceramics or mixtures of these, are used.
  • the optimum amount of catalytically active metal i.e. cobalt, depends on the support material used.
  • the content of cobalt in the catalysts used in the context of the present invention is between 1 and 100 parts by weight per 100 parts by weight of support material, preferably between 10 and 50 parts by weight per 100 parts by weight of support material.
  • the catalysts used in the context of the present invention may further comprise one or more metallic promoters or co-catalysts. These may be present as metal or as metal oxides. Suitable promoters include oxides of metals of Groups IIA, IIIB, IVB, VB, VIB and VIIB of the Periodic Table of the Elements and oxides of lanthanides and/or actinides. For example, based on titanium, zirconium, manganese and/or vanadium. Alternatively or in addition to the metal oxide promoters, the catalysts may comprise metallic promoters selected from Groups VIIB and/or VIII of the Periodic Table of the Elements. For example, rhenium, platinum and/or palladium. Typically, the promoter content, if any, in the catalysts used in the present invention is between 0.1 and 60 parts by weight per 100 parts by weight of support material, this content may vary widely within the mentioned limits depending on the exact promoter material used.
  • a catalyst based on cobalt as the catalytically active metal and comprising manganese and/or vanadium as promoters is well suited.
  • An example of this is a catalyst in which the atomic ratio of cobalt to promoter is at least 12:1.
  • the size of the catalyst particles used in the present invention also depends on the exact reactor. For example, in microreactors often catalysts with smaller particle sizes are used.
  • catalysts having an average diameter of 0.5 mm to 15 mm are used.
  • the catalysts can also be extrudates, in which case they have, for example, a length of 2 mm to 10 mm, in particular 5 mm to 6 mm, and a cross-sectional area of 1 to 6 mm2, preferably 2 to 3 mm2.
  • the weight ratio of the catalyst amounts, in a process with two fixed-bed synthesis reactors, a weight ratio between 1.1:1 and 4.3:1, preferably 1.2:1 and 4.3:1, catalyst amount in the first fixed-bed synthesis reactor to catalyst amount in the second fixed-bed synthesis reactor is set in the context of the present invention. In particularly preferred variants, the weight ratio is set at 1.25:1 to 2.5:1.
  • a particularly preferred weight ratio in the context of the present invention is 2:1.
  • the origin of the synthesis gas is in principle not limited.
  • the synthesis gas can be obtained from gasification of biomass, from synthesis gas generation from fossil starting materials (natural gas, crude oil, coal), or from electricity-based processes (conversion of electrolytically generated H 2 as well as CO 2 ).
  • the product separation is carried out in multiple stages. More suitably, a multi-stage product separation comprises at least one hot separator and one cold separator.
  • the hot separator is operated at a temperature of 160 to 200° C., for example about 180° C.
  • cold separator is operated at a temperature of 0 to 20° C., for example 10° C.
  • water is additionally separated during the product separation.
  • the separated reaction water can be reused in the process.
  • the molar ratio of H 2 to CO in the synthesis gas is adjusted to a ratio of 1.7:1 to 2.3:1, preferably 1.8:1 to 2.3:1, particularly preferably 1.9:1 to 2.3:1.
  • it is adjusted to a molar ratio selected from the group consisting of the ratios 1.8:1, 1.9:1, 2.0:1, 2.1:1, 2.2:1 and 2.3:1.
  • the present invention is not limited to these. Of course, the present invention also encompasses ratios lying between these values.
  • the first fixed-bed synthesis reactor is preferably operated in such a way that the selectivity for the end products (preferably long-chain hydrocarbons in certain quantities also (terminal) alkenes) is particularly high.
  • the double bond present enables further growth of the hydrocarbon chain in the subsequent second fixed-bed reactor stage through readsorption of the hydrocarbons on the catalyst. Unsaturated long chain hydrocarbons separated in the product separation may require subsequent treatment with hydrogen to hydrogenate the double bond(s).
  • the preferred goal of the operation of the second fixed-bed synthesis reactor is the reaction of remaining synthesis gas and the conversion of the short-chain and shorter-chain hydrocarbons from the first fixed-bed synthesis reactor to proportionally as many long-chain hydrocarbons as possible.
  • shorter-chain hydrocarbons chain length: C 5 -C 24
  • a gas fraction of light short-chain hydrocarbons (C 1 -C 4 ) and residual gases (CO, CO 2 , H 2 ) are produced in the second product separation.
  • Most of the oxygen-containing hydrocarbons by-products: alcohols, organic acids, . . . ) are dissolved in the aqueous phase.
  • reaction conditions in the first and second fixed-bed synthesis reactors, as well as all further fixed-bed synthesis reactors, are adjusted within the scope of the present invention for conversion control by controlling the reactor temperature to an equal value between 180° C. and 250° C. in all synthesis reactors depending on the desired, between 40 and 90 mol %, total CO conversion.
  • the reactor temperatures in all fixed-bed synthesis reactors are controlled to an equal value between 200 and 240° C., particularly preferably 200 to 230° C., in particular preferably 200 to 220° C., even more preferably 200 to 210° C., wherein the values are to be considered with a tolerance of plus/minus 3° C., respectively.
  • the temperature can be set to a value selected from the group consisting of 200° C., 205° C., 210° C., 215° C., 220° C., 225° C., 230° C., 235° C. and 240° C.
  • a value selected from the group consisting of 200° C., 205° C., 210° C., 215° C., 220° C., 225° C., 230° C., 235° C. and 240° C.
  • the present invention is not limited to these.
  • the present invention also encompasses temperatures lying between these values; the values mentioned are merely simple control steps. Stepless control is equally possible.
  • the inert gas content of the synthesis gas fed in the context of the present invention is between 0 vol. % and 50 vol. %. It is preferred if the inert gas content is between 0 and 40 vol. %. Specific values for the inert gas content in the synthesis gas are selected in variants of the present invention from the group consisting of 0 vol. %, 5 vol. %, 10 vol. %, 15 vol. %, 20 vol. %, 25 vol. %, 30 vol. %, 35 vol. % and 40 vol. %. In this regard, it should be appreciated that while certain preferred percentages are mentioned herein, the present invention is not limited to these. Of course, the present invention also encompasses percentages lying between these values.
  • the weight volume flow rate (WHSV(CO)) for Fischer-Tropsch syntheses in the context of the present invention can, for example, be set to values between 0.1 and kgCO/(kgKat*h). It is essential that it is set to an input value and this is then not changed during the ongoing process, but left constant during the process. There is also no readjustment in this respect between the individual stages. Minor fluctuations caused by the equipment in the weight volume flow at the input are harmless.
  • the first fixed-bed synthesis reactor is operated at a pressure of 15 to 30 bar, preferably 19 to 25 bar, in particular 22 bar and, independently thereof, and the second fixed-bed synthesis reactor at a pressure of 15 to 30 bar, preferably 17 to 23 bar, in particular 20 bar.
  • the first reactor operates at the highest pressure and the subsequent reactors each have a slightly lower pressure than the immediately preceding reactor.
  • the pressure in the entire apparatus is adjusted by a single pressure control device, in particular located downstream of the last reactor.
  • a single pressure control device in particular located downstream of the last reactor.
  • the molar H 2 :CO ratio in the synthesis gas, the inert gas proportion in the synthesis gas, the quantitative ratio of the catalysts to each other, the pressure in the first fixed-bed synthesis reactor and the pressure in the second fixed-bed synthesis reactor, as well as the weight volume flow rate are kept constant.
  • the control of the conversion is in particular possible very precisely. It is not mandatory to keep all these parameters constant. However, in this way the control is best. In particular, in this way the synthesis process is very well controllable and easy to monitor. This represents a great advantage in terms of equipment and organisation, because an effective and reliable process control is possible via a few controllers and with few personnel. Automation is also much easier to realise in this case.
  • the molar H 2 :CO ratio it is highly preferred in the context of the present invention to set the molar H 2 :CO ratio to a value within the ranges mentioned and to keep it constant during the process, in particular to a ratio between 1.9 and 2.4, preferably 2.0 and 2.4, more preferably 2.0 to 2.3, in particular 2.1.
  • the values are to be regarded in each case with a tolerance of plus/minus 0.3, particularly preferably with a tolerance of 0.1, in particular without tolerance, i.e. only with fluctuations due to measurement technology.
  • the molar H 2 :CO ratio is set to a value within the ranges mentioned and to keep it constant during the process, in particular to a ratio between 1.9 and 2.3, preferably 2.0 and 2.3, more preferably 2.1 to 2.3, even more preferably 2.2 to 2.3 and most preferably 2.3.
  • the values are in each case to be regarded as having a tolerance of plus/minus 0.1, preferably 0.05, in particular without tolerance, i.e. only with fluctuations due to measurement technology.
  • the hydrogen conversion considered over all stages, it is at most 99 mol %, preferably at most 98 mol %, particularly preferably at most 97 mol %, especially preferably at most 96 mol % and most preferably at most 95 mol %.
  • a hydrogen conversion of at most 98 mol %, or at most 97 mol %, or at most 96 mol %, or at most 95 mol %, considered over all stages, is controlled.
  • a product stream leaving the second fixed-bed synthesis reactor comprising long chain hydrocarbons is fed to a second product separation to separate a fraction of long chain hydrocarbons from the product stream.
  • water is preferably also separated.
  • the product stream leaving the second product separation comprising short-chain hydrocarbons can be fed to a further fixed-bed synthesis reactor.
  • the yield of the target product can be maximised in the power-to-liquid process, in which CO 2 is converted into the target product together with renewable, electrolytically produced hydrogen.
  • This is particularly important because the energetically expensive process routes for providing the reactants, especially H 2 via electricity-based processes such as electrolysis, or CO 2 in the case of capture from e.g. the air, require a most efficient and targeted conversion possible into target product so that these processes can be carried out in an economically attractive manner.
  • the efficiency of a power-to-liquid plant is measured in terms of the amount of target product per electricity expended.
  • conversion control can be implemented relatively easily through the measures mentioned above.
  • a simple intermediate separation of the products of the first reactor is already provided for.
  • the continuation of the C 5 -C 24 fraction into the next stage is thus possible with only minor modifications to existing systems.
  • the increase in the yield of long-chain hydrocarbons, in particular of the very valuable C 25 hydrocarbons, can thus be increased by adapted reaction and separation conditions with relatively little effort.
  • Particularly preferred variants of the present invention relate to a conversion of 50 to 60%, a molar H 2 :CO ratio of between 1.9:1 and 2.3:1, an inert gas content of 0 to 40 vol. % and a weight ratio of the catalysts of 1.25:1 to 2.52:1, as well as a pressure in the first reactor of 18 to 26 bar and in the second reactor 16 to 24 bar.
  • the present invention also relates to a plant for carrying out the method described above, comprising
  • the plant of the present invention comprises a further product separation A) serially connected downstream of the second fixed-bed synthesis reactor, which is designed to separate a fraction of long-chain hydrocarbons from a product stream leaving the second fixed-bed synthesis reactor.
  • each fixed-bed synthesis reactor may comprise one or more apparatuses B) connected in parallel, wherein these are preferably characterised by an identical architecture.
  • the plant of the present invention comprises one or more further reaction stages C) which are connected in series downstream of the first and/or second reaction stage comprising a fixed-bed synthesis reactor as well as a product separation.
  • the first and/or the second fixed-bed synthesis reactor is preferably a micro structured fixed-bed synthesis reactor.
  • the first and the second fixed-bed synthesis reactor preferably have the same architecture.
  • a subject matter of the present invention is a method for controlling the CO conversion in multi-stage Fischer-Tropsch syntheses, in which synthesis gas is only added to the first synthesis reactor, to between 40 and 90 mol %, preferably 50 to 80%, in particular 50 to 60 mol %, by continuously and simultaneously adjusting the reactor temperatures for all Fischer-Tropsch synthesis reactors to an equal value between 180° C.
  • weight volume flow at the inlet of the FTS is adjusted to a value and kept constant at this value during the process, wherein preferably the parameters mentioned below are set and kept constant during the synthesis process: molar H 2 :CO ratio in the synthesis gas of 1.7:1 to 2.3:1, inert gas content in the synthesis gas between 0 and 40 vol. %, same cobalt-based Fischer-Tropsch catalyst in all reactors, weight ratio of the amount of catalyst of first fixed-bed synthesis reactor to second fixed-bed synthesis reactor between 1.2:1 and 4.3:1, pressure in the fixed-bed synthesis reactors 10 to 50 bar in each case, hydrogen conversion considered over all stages at most 99 mol %.
  • the CO conversion is controlled to the desired value by adjusting the reaction temperature in all reactors to the same temperature.
  • a prerequisite in the context of the present invention is that the other parameters mentioned are kept constant.
  • Particularly advantageous in the present invention is that in this way the course of the reaction can be kept very constant, and the resulting amount of valuable product can be precisely planned.
  • this method it is possible to selectively change the product distribution during the ongoing process if, e.g., a certain fraction of the product mixture is under- or over-represented compared to the currently desired ratio.
  • control of CO conversion according to the present invention is an immense advantage in terms of equipment and process technology, as it is relatively easy to achieve cooling of all reactors to the same temperature. This can be achieved, for example, by selectively arranging all reactors in a heat exchanger complex.
  • Another surprising and advantageous effect of the present invention is that a very good reaction and process control is possible, although there is no addition of synthesis gas after the first reactor. Contrary to expectations, good controllability is achieved despite the lack of intermediate stage control or intermediate stage readjustment. Based on the prior art, it was not to be expected that by the measures according to the invention or the procedure according to the invention a precise control of the Fischer-Tropsch synthesis in a simple manner would be possible.
  • control of the conversion or the possibility to keep the conversion specifically adjusted to a constant value is very effective with the method according to the invention and the plant according to the invention and much simpler than an adjustment of the catalyst amounts.
  • the weight volume flow is kept constant at the inlet of the AGV. This is a great advantage in that by this and the control via the temperature the integration into further (industrial) processes is considerably facilitated. For it is not at all unusual that other processes, for example synthesis gas production, provide a constant weight volume flow. In the context of the present invention, this can then simply be fed directly on to the FTS.
  • the present invention is described in this description essentially with reference to two fixed-bed synthesis reactors, the present invention is expressly also related to methods and plants comprising more than two fixed-bed synthesis reactors, wherein a fixed-bed synthesis reactor is then each time followed by a product separation apparatus or product separation step.
  • a fixed-bed synthesis reactor is then each time followed by a product separation apparatus or product separation step.
  • multi-stage processes and plants with five fixed-bed synthesis reactors, four fixed-bed synthesis reactors, or three fixed-bed synthesis reactors.
  • FIG. 1 is a diagrammatic representation of FIG. 1 :
  • a synthesis gas stream comprising H 2 and CO 11 is fed at a constant weight volume flow into a first fixed-bed synthesis reactor 1 , in which H 2 and CO are catalytically converted to hydrocarbons.
  • a product stream 12 leaving the first fixed-bed synthesis reactor 1 is fed into a (first) separation device 2 , in which a fraction of long-chain hydrocarbons is separated 2 a .
  • the remaining fractions, comprising essentially short and shorter chain hydrocarbons, CO, CO 2 and H 2 , as well as possibly residues of H 2 O 13 are fed into a second fixed-bed synthesis reactor 3 , and catalytically converted to long chain hydrocarbons (>C 25 ) 3 a.
  • FIG. 2
  • a synthesis gas stream comprising H 2 and CO 11 is fed at a constant weight volume flow into a first fixed-bed synthesis reactor 1 , in which H 2 and CO are catalytically converted to hydrocarbons.
  • a product stream 12 leaving the first fixed-bed synthesis reactor 1 is fed into a (first) separation device 2 , in which a fraction of long-chain hydrocarbons, as well as an aqueous fraction is separated 2 a .
  • the remaining fractions, comprising essentially short and shorter chain hydrocarbons, CO, CO 2 and H 2 13 are fed into a second fixed-bed synthesis reactor 3 , and catalytically converted to essentially long chain hydrocarbons.
  • a product stream 3 a of the second fixed-bed synthesis reactor 3 is fed to a second product separation 21 , in which the fraction of long chain hydrocarbons 21 a is separated from the fraction comprising short and shorter chain hydrocarbons (C 1 -C 24 ), CO, CO 2 and H 2 , 21 c as well as an aqueous fraction 21 b .
  • the aqueous fraction 21 b can be combined with the aqueous fraction from the first product separation 2 b .
  • the fraction of long-chain hydrocarbons 21 a separated by means of the second product separation is combined with the fraction of long-chain hydrocarbons 2 a from the first product separation.
  • FTS was carried out with two reactors connected in sequence according to the invention, each using the same cobalt-based catalyst.
  • temperature, target conversion, H 2 :CO ratio, inert gas content were set differently and the individual results were tabulated, wherein the values in the table indicate the required catalyst mass ratio of catalyst mass in the first fixed-bed synthesis reactor to catalyst mass in the second fixed-bed synthesis reactor in order to achieve the respective conversion as a function of temperature.
  • the following table shows a design matrix in which the experimental data of the process discussed above are entered.
  • the matrix has been divided into several pages for better readability.
  • the temperature was outlined in steps of 200° C., 210° C., 220° C., 230° C. and 240° C. against the molar CO conversion in steps of 50 mol %, 60 mol %, 70 mol %, 80 mol %.
  • the molar H 2 :CO ratio was outlined in steps of 1.8:1 1.9:1 2.0:1 2.1:1, 2.2:1, 2.3:1 against the inert gas fraction in steps of 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%.
  • Values marked with an asterisk are values where the hydrogen conversion increased to above 99 mol %. If the values in the table are marked with “0*”, this means that complete hydrogen conversion already took place in the first stage.
  • the optimal ratio of the catalyst amounts is between 2.52:1 and 1.25:1.
  • reaction can be easily controlled by adjusting the temperature.

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  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
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US18/555,047 2021-04-27 2022-04-13 Co conversion control for multistage fischer-tropsch syntheses Pending US20240124373A1 (en)

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DE102021110735.0A DE102021110735A1 (de) 2021-04-27 2021-04-27 Verfahren zur Herstellung von Kohlenwasserstoffen
DE102021110735.0 2021-04-27
PCT/EP2022/059829 WO2022228896A1 (fr) 2021-04-27 2022-04-13 Contrôle de la conversion du co dans des synthèses de fischer-tropsch en plusieurs étapes

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US5028634A (en) * 1989-08-23 1991-07-02 Exxon Research & Engineering Company Two stage process for hydrocarbon synthesis
US6156809A (en) * 1999-04-21 2000-12-05 Reema International Corp. Multiple reactor system and method for fischer-tropsch synthesis
US20040102530A1 (en) * 2002-11-22 2004-05-27 Blue Star Sustainable Technologies Corporation Multistage compact fischer-tropsch reactor
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RU2409608C2 (ru) 2005-07-20 2011-01-20 Шелл Интернэшнл Рисерч Маатсхаппий Б.В. Многостадийный способ фишера-тропша
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